(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
See other formats

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

298                                ALASKAN GLACIER STUDIES
was sensibly felt by the whole party, although the ground on which they were was at least two leagues from the spot where the fall of. ice had taken place."
Harvard Glacier. Harvard Glacier, at the head of College Fiord, is an ice tongue certainly over 8 miles in length and probably at least twice as long. It heads on a divide at the crest of the Chugach Mountains and from the same pass Matanuska Glacier flows northward.1 Harvard Glacier has a width ota mile to a mile and a quarter in the portion near the terminus and is fed by six good-sized tributary glaciers in the lower 6 miles, while many other tributaries enter above from cirques east of Mt. Grant.8 The lower tributaries are all cascading glaciers, the only ones named being Radcliffe, Eliot,3 and Lowell8 glaciers. These cascading tributaries have an average slope of 165 to 2400 feet to the mile in their lower course, while the average slope of the lower 4J miles of the main ice tongue is only 700 feet per mile. Harvard Glacier ends in a tidal ice cliff 350 feet high in 1899, the eastern part being lowest in 1910, as in 1899. That the glacier end is not afloat is proved by the fact that a half mile from the terminus the fiord is only 636 feet in depth.
The surface of the main glacier (PI. CXTV, A) is severely crevassed throughout its whole visible extent, and upon it are eight prominent medial moraines, most of which can be traced backward to a point where they enter as lateral moraines from the margins of tributary glaciers. There are also several subordinate medials near the east side of the glacier. The position of the medial moraine formed by the north lateral moraine of the Radcliffe Glacier, indicates that in 1910 the Radcliffe was almost as strong as the main Harvard Glacier above the junction; for this medial moraine reaches the terminal cliff of Harvard Glacier nearly in the middle, showing that at least in the upper layers the ice from Radcliffe Glacier compresses the Harvard stream to half of its normal width. This is also shown in a unique way by the cross-section of all of the medial moraines revealed on the precipitous front of Harvard Glacier. These moraines, whose rock fragments darken the otherwise-white face of the cliff from top to bottom, are not vertical in cross-section (PL CXIV, B), but are inclined at angles of from 70° to 22°. The fact that the top of each inclined moraine section is farther east than the bottom, indicates that the push of the Radcliffe Glacier which comes in from the west is responsible for this inclined position.
It is possible that the reason why the Radcliffe Glacier is able to dominate the larger Harvard ice tongue is because the Radcliffe has so much steeper slope than the Harvard, Its slope is not much steeper than the other tributaries like the Eliot Glacier, but the descent in a short distance is greater. It may be that this is only a superficial influence, that is, that Radcliffe Glacier flows out and rides upon the surface of Harvard Glacier because of some rather recent advance.
There is a broad lateral moraine on each side of Harvard Glacier, the two lateral moraines at the terminus being respectively the south laterals of the Radcliffe and Lowell Glaciers, while the lateral moraines farther north on Harvard Glacier are diverted successively and become medial moraines below the entrance of each of the tributaries.
i See PI. I, Bull. 827, U. S. Geol. Survey, 1907. *Named in 19iO for Prof. U. S. Grant of Northwestern University,
»Named in 1910 for Charles W. Eliot and A. Lawrence Lowell, the former president and the present president of Harvard University,